A design rule is a list of constraints that must be satisfied by a technical device such as an integrated circuit. For example, conductors in a circuit may be required to be separated from each other by a certain minimum distance. There also may be constraints concerning the size and the shape of circuitry. A design rule can be rather complex, firstly because of the number of parameters involved and secondly due to the fact that a certain requirement such as the minimum distance between two conductors may depend on parameters such as the thickness of these conductors or their curvature. A design rule checking (DRC) tool therefore needs to be tested before it is used to make sure that the DRC tool, when applied to a given design, will detect any violation of a design rule. Missed violations of design rules often lead to silicon failure. Attempts have therefore been made to devise reliable methods for the testing of design rule checking tools.
A DRC tool may be tested using a large number of test layouts (test cases) that comprise test cases in accordance with the design rule to be tested as well as cases violating the design rule. For a design rule that comprises N different design constraints, for example, one test case per design constraint may be created so that each test case violates exactly one design constraint of the design rule. The present disclosure was motivated by the realization that such a set of test cases may be incomplete.